The invention relates to a pneumatically-operating impact tool and a method for operating a pneumatic impact tool.
Pneumatically-operating impact tools are especially used for dislodging or knocking deposits off a tank wall, or the like. For example, it may be a case of knocking scale or dusty material off a tank wall. Pounding or knocking of this type has proven to be effective and sometimes necessary if the dusty material is not completely dry and also has a tendency to form channels or deposits. By using a forceful impact against the outer wall of the tank, it is possible to loosen and/or release the debris or dusty material and cause it to flow out.
A pneumatically-operating impact tool and a method for operating a pneumatically-operating impact tool are known from DE 38 19 112 A 1. With an impact tool such as this, the impact piston is moved away from the impact plate and/or the tank wall by application of an excess pressure applied to the first pressure chamber and a strong spring that is arranged between the impact piston and the cover which is compressed.
After the switching of a valve assigned to the first cylinder chamber into the vent or ventilating setting, this spring has the task of moving the impact piston abruptly against the impact plate and/or the tank wall and thus causing the impacts. A quick-action ventilating valve arranged in the area of the cover vents the first pressure chamber to the second pressure chamber holding the spring, so that the air leaving the first compression chamber is transferred to the second compression chamber and, with a low force percentage, overcomes the spring force.
With this impact tool, the disadvantage is that the design is very complicated, because the spring has to be positioned between the impact piston and the cover, and a quick-action ventilating valve must be provided and integrated into the cover. Consequently, the manufacturing effort for this impact tool and also the assembly effort are considerable. If it is taken into consideration that hard impact forces are exerted by means of the impact tool, there is an increased susceptibility to malfunction among the large number of individual parts of the impact tool, since each individual component of the impact tool is subject to a high introduction of force and vibratory stresses.
A similarly designed pneumatically-operating impact tool with a spring arranged between the impact piston and the cover is known from DE 38 19 111 A 1.
A pneumatically-operating impact tool with a spring is also described in DE PS 2 49 551. In it, the air channel between the first pressure chamber and the second pressure chamber is guided outside the cylinder pipe.
U.S. Pat. No. 4,070,947 describes a pneumatically-operating impact tool and a method for operating a pneumatically-operating impact tool, in which a cylinder pipe is used to guide an impact piston, whereby the cylinder pipe is closed with a cover, and a pressure chamber is formed between the impact piston and the cover. This cover is provided with an opening that is connected to a compressed air connection. The cover plate has the task of delimiting the pressure chamber and serving as a stop for the impact piston. In its end position, moved away from the impact plate, the impact piston does not seal the opening. The driving of the piston in the direction of the impact plate occurs by opening a valve and thus application of an elevated pressure on the impact piston, and in fact directly with respect to its entire piston surface.